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In the Aptio UEFI Firmware on my Windows 8.1 Asus Laptop, under Advanced Settings there’s a setting named ‘OS Selection’ and options are ‘Windows 8.x/Windows 7’.

I am trying to understand what’s the exact purpose of this setting and how it matters? There’s no info available within Firmware Help and nothing much is found online.

I did seek Asus support, but except for very basic & obvious explanation to set this as per intended OS there was no further explanation.

I though may be setting it to Windows 7 might be disabling Windows 8 exclusive features in the firmware like Fast Boot, Secure Boot etc but they are still totally independent.

Does anyone know how that setting really works? What different it does when set to Windows 7 and Windows 8.x?

Thanks.

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I have the same settings in the UEFI firmware of a Medion laptop. No explanation either. But with the setting on windows 8.x the laptop fails to run the windows 7 installer with a red bar at the top of the screen as described here: I get a red bar when trying to install windows 7 dvd and it freezes.

At least on the Medion the setting seems to do two things:

  1. In windows 7 mode it:

    • Disables secure boot.
    • Enables or emulates the VGA option ROM (BIOS interrupt 10H)
  2. In windows 8 mode it:

    • Enables secure boot (which you revert to disabled immediately after changing this setting).
    • Uses the UEFI Graphics Output Protocol), which is not compatible with windows 7.

It might do more than that, but there is no help in my firmware either and no mention of anything like it in the manual.

The UEFI firmware ysed in my Medion laptop was called "aptio setup utility" with "BIOS version 6.13" and below that is "GOP version 7.1.1003". The latter is something I only noticed today.

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  • I got a fair idea from your answer and the related links. Thank you Hennes for your inputs. I am however still a bit puzzled. On my Asus X200MA, Secure Boot & Fast Boot are controlled by the CSM Switch and not the OS Selection. Moreover now if I correctly understand, in my laptop, it’s the CSM Switch that as well controls whether to use vBIOS or GOP. With CSM Enabled, I see vBIOS Version in the setup’s home screen and when CSM Disabled it shows GOP version. That makes me wonder if CSM is already controlling choice of Graphics protocol, why a separate OS Selection is needed?
    – patkim
    Oct 4, 2016 at 13:52
  • Good question. Sadly no answer here. Personally I would have used a switch "graphics boot:" with as option "BIOS int 10 (Win7 compatible)" and "GOP (modern)". But laptop firmwares also seem rather basic to me (I am used to gaming/OC boards. And not because I game or overclock but because they ship with normal/decent features).
    – Hennes
    Oct 4, 2016 at 13:56

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